Hi. im a new member of this community. i have a doubt in the subject that human phenotypic characers and its controlled genes.. ive observed tht many has attached earlobe whereas some has free.. and some can roll their tongue in "u" direction, whereas others cant.. and, some can bend their thumbs backward, while most of the people cant....... wht is all behind these? my teacher said me that these are the result of the play of genes.. but it isnt clear to me.... ive also searche the net but couldnt gather any more.. can any one of youu tell me the mechanisms involved in these? which genes on which chromosomes are controlling these? which stasis is shown by them? are the sex-linked? can u plz explain all these phenomena....